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The Splendid Table's How To Eat Supper By Lynne Rossetto Kasper

Dear Lynne,

How long should I marinate things? Some recipes say only, "marinate," with no time frame. Obviously a big roast has to marinate longer than a fish filet, but how much time is too long, or too short? And how many times can you use a leftover marinade?

Kane and Russell from Idaho

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Dear Kane and Russell,

Great questions here because marinades are complicated. Most important, never, ever reuse a leftover marinade because it can have harmful bacteria.

As for timing, a couple of guiding forces come into play. First, a marinade never totally penetrates most foods. Brines, which are based on salt do that. Marinades, at best, flavor a thin outside layer unless the food is very thin like shavings of carrot, fish filets, and the like. So the thinner the food is cut the less time it needs in a marinade.

You also want less time if you're using a high-acid marinade because the acid breaks down tissue and can toughen meats. So when there's a lot of vinegar, wine, citrus and the like in proportion to other ingredients cut back on soaking time.

When a marinade's high in fats, it tends to moisten, and to some extent so does sugar. So here you have leeway. For instance with the Thai coconut milk marinade recipe below, you could marinate chicken thighs (which have their own moistening fat) overnight. Chicken breasts, because they are thin and lean, would need only one or two hours.

A Marinade Timing Guide

Always marinate in the refrigerator and never reuse a marinade as it can carry harmful bacteria. Food poisoning is not fun. If you're basting with the marinade, stop well ahead of the food being done. This way any raw meat, fish or poultry juices in the marinade can cook away before the food is done.

• Fish and Seafood: 15 to 30 minutes for small pieces; 30 minutes for thicker ones.

• Tempeh, Tofu, and Seitan: For tofu and other fragile soy foods, 30 minutes to an hour. For the denser, firmer seitan and tempeh, 30 minutes to several hours.

• Fruits: Most fruit sauces act as marinades. Sugar draw moisture out fruits, while acids break down their structure. Sometimes you want both in making a fruit sauce for instance.

Thai Coconut-Ginger Marinade 15 minutes prep time Hold in the fridge up to 3 days, or freeze up to 4 months

This is one of those recipes you'll use a lot. I fool with the combination all the time, changing the balance of ingredients and adding and subtracting seasonings.

Suave coconut milk moistens and gently flavors while the fish sauce brings salt and umami into the mix. Ginger, garlic, chile and lime are the high, bright exclamation points. To keep the acid low, the lime is subtle here, but once whatever you're cooking is done, give it extra snap with a squeeze of fresh lime.

Cook to Cook: Marinate any meat, bird, fish or soy food in this -- chicken thighs are especially fine here. Thin sliced carrots and sweet potatoes grill up brilliantly after an hour in the mix.

A friend uses the marinade for catfish filets, then she grills them with strips of marinated sweet peppers, or batters them and fries the fish like chicken. So good.